The present invention is in the field of plastic films or sheets, especially perforated plastic films and is particularly concerned with sterilizable packaging material and packages made therefrom. Such packages are used as containers for sterile gauze and other types of wound dressings. The present invention is more particularly related to a material for packaging articles which can be sterilized after packaging.
In the medical field there are numerous applications and demands for sterile articles. Such articles include wound dressings such as gauze, cotton, and the like, and surgical instruments such as needles, scalpels, clamps, and the like. When packaging these materials, difficulties are encountered in maintaining the articles in a sterile condition while placing them in a package which will maintain the sterile condition. If an item must be handled by a packaging machine or packaging personnel after it is sterilized, there is the danger that the person or machine handling the item prior to packaging will contaminate the item.
Perforated plastic films having many useful applications, such as the manufacture of disposable diapers or other absorbent structures and in the packaging of foods or other materials.
Perforated plastic films have a plurality of relatively small or minute perforations therein with the perforations being located in small protuberances constructed in the film. Such perforated film generally has about 30 to about 1500 perforations per square inch or even more. The holes are of varied geometrical configurations, for example, rectangular or square shaped, pentagonal, hexagonal or other shape. The protuberances are also of various shapes, but are usually cone shaped or pyramid like.
One method of making perforated thermoplastic sheet or film is disclosed in U.S. Pat. No. 3,054,148, issued to Zimmerli. The patent discloses a stationary drum having a molding element mounted around the outer surface of the drum which is adapted to rotate freely thereon. A vacuum chamber is employed beneath the screen or molding element to create a pressure differential between the respective surfaces of the thermoplastic sheet to cause the plasticized sheet to flow into the perforations provided in the molding element and thereby cause a series of holes to be formed in the sheet.
Types of screens or molding elements are illustrated in U.S. Pat. No. 4,155,693.
U.S. Pat. No. 4,262,516 and U.S. Pat. No. 4,317,792 disclose apparatus and method, respectively for manufacturing thermoplastic sheet or film having elliptical holes.
It is highly desirable that a material be provided for making a package which can be used to maintain items in a sterile condition in which the items can be sterilized while actually inside the package.
In some cases even if sterilization standards are maintained, contamination can still occur when fibers break away from conventional packaging material such as coated paper and non-woven sheets made from polyolefin fibers. Such fibers can be dangerous if they should enter the sterile field and become entrapped in a wound or incision and thereby provide a situs for infection or irritation.
It is even more desirable that a non-fibrous material be provided for making the package which can be used to maintain items in a sterile condition and in which the items can be sterilized while actually inside the package.
It is therefore a primary object of the present invention to provide an aseptic package and materials and method for constructing the package.